fix test

aiida_mlip/calculations/train.py

@@ -48,7 +48,7 @@ def validate_inputs(
             if not ((Path(config_file.as_dictionary[key])).resolve()).exists():
                 raise InputValidationError(f"Path given for {key} does not exist")
         # Check if fine-tuning is enabled and validate accordingly
-        if "fine_tune" in inputs:
+        if inputs["fine_tune"] is True:
             if "foundation_model" not in config_file and "model" not in inputs:
                 raise InputValidationError(
                     "Undefined Model to fine-tune in inputs or config file"